JPH0652083B2 - Self-tapping pin screws for screwing into aerated concrete - Google Patents

Description

The present invention relates to a self-tapping pin screw for screwing into aerated concrete, which has at least 1.
It has a diameter of 5 times and is of a type in which the thread profile limited by the two busbars is asymmetric with respect to a plane perpendicular to the axis of the screw.

[Conventional technology]

From DE-OS 2912924, there is already known a tatsupin screw for porosity concrete in which the apex of two thread crests is recessed in an arc shape when viewed in a longitudinal section including a screw axis. However, with this screw, the threads are not tightly engaged in the material so that a large tensile load does not result in a large resistance in the porous concrete or cellular concrete.

Further, from DE-OS No. 3114138, one in which the radial length of the thread flank, which is oriented toward the screw head and which supports the tensile force, is oriented toward the tip of the screw, which does not support the tensile force. Self-tapping pin screws are known which are longer than the radial length of the thread flanks. In this case, the average flank inclination angle of the thread flanks facing the screw head is relatively gentle, and as a result, the component force generated when a tensile load is applied to the inserted screw is relative to the central axis of the screw. And forms the same gentle angle as the above flank inclination angle. This significantly reduces the force required to pull out such screws when they are used in porous concrete or cellular concrete.

Furthermore, according to DIN standard 58810, it is known to form a thread profile asymmetrically with respect to a plane perpendicular to the axis of the screw. The thread flanks facing the screw head are limited by the generatrices lying in the plane. On the other hand, the generatrix of the thread flank facing the screw tip is arcuately transferred to the core section.
This provides a bearing surface perpendicular to the axis of the screw in the tension direction of the screw. In this configuration, in fact, when a tensile load is applied to the screw, the force acts parallel to the axis of the screw, so that the aerated concrete section located between the threads is sheared without significant resistance. It is inconvenient to use this screw for aerated concrete, as it will be done.

[Problems to be Solved by the Present Invention]

The object of the invention is to create a special compaction of the material in the region of the cellular concrete which is to receive the tensile load and to ensure a relatively large interlocking engagement between the screw and the surrounding material. Another object of the present invention is to provide a self-tapping pin screw particularly suitable for use in aerated concrete.

[Means for Solving the Problems]

SUMMARY OF THE INVENTION According to the invention, in the self-tapping pin screw of the type mentioned at the beginning of the invention, the generatrix of the thread flank facing the screw head is at least partially arcuate or parabolic from the crest of the thread to the core. Formed of a number of straight or substantially arcuate or parabolic curved sections extending or possibly connected to each other stepwise, and further of a thread flank facing the cutting edge. The busbar is almost zero with respect to the plane perpendicular to the screw axis.
It is solved by the fact that it is formed by a straight line forming an angle of 25 °.

[Action and effect]

According to the above-mentioned means according to the invention, the range in which the screw used is subjected in particular to a tensile load is significantly more compacted than the range opposite the thread flank facing the screw tip. . Since only a tensile load is actually applied to this type of screw, it is sufficient if a suitable stability is obtained in the pull-out direction. For this reason, a thread having a slender cross section is formed, although a bus bar extending in an arc or parabola is formed on one side for one thread flank. As a result, a relatively large portion of the material surrounding the screw becomes engageable between the threads.

Furthermore, according to the special configuration of the invention of the thread flank facing the screw head, the component force that must be received in the cellular concrete by the surrounding material during tensile loading of the screw is that of the screw. It acts outwards at a relatively large angle with respect to the central axis, which makes it possible to transmit forces to the material parts located laterally of the screw used.
Furthermore, according to the invention, the thread volume is slightly increased by the special thread shape, and the pull-out resistance value is increased even though the total volume of the screw itself is almost the same as that of the known screw with which comparison is possible. Remarkably increased.

In order to get the best configuration for screwing into cellular concrete, the special configuration of the above screws is important. Due to its low compressive and shear strengths compared to other materials, any trivialities need to be utilized in order to obtain the best effect and stability for securing the screw. Furthermore, in this case, it would be advantageous if the screw could be screwed directly into the aerated concrete body, i.e. without using a cut and expansion plug.

〔Example〕

 The invention will now be described with reference to the illustrated embodiment.

According to FIGS. 1 to 3, the screw 1 is a shaft 2,
It is formed from a screw head 3 and a cutting point 4. The screw shaft 2 can be provided with a thread section 5 over part of its length or over its entire length. In the embodiment shown in FIG. 1, a threadless section 6 is provided between the screw head 3 and the thread section 5.

The outer diameter Da is at least 1.5 times the core diameter Dk in order to screw the thread section 5 into the cellular concrete material relatively deeply.

According to the exemplary embodiment shown, the thread flank 7 facing the screw head 3 moves from the thread crest 8 to the core,
It is limited by a generatrix extending in an arc, this transition taking place along the radius of curvature R in FIG. The thread flank 7 faces the threaded head 3. Cut 4
The thread flank 9 facing towards is restricted by a generally straight busbar and makes an acute angle α of about 10 ° with respect to a plane 11 perpendicular to the axis 10 of the screw.
This angle α is preferably in the range of approximately 0 ° to 25 °. Therefore, in the range of the thread flank 9 facing the screw tip portion, the body weight occupied by the thread section 5 is small, and as a result,
The cross-section of the aerated concrete that penetrates between the threads is relatively large. Thread flank 7 facing the screw head 3
With a special construction of, an average flank tilt angle β of approximately 60 ° is obtained for a plane 11 perpendicular to the axis 10 of the screw. Thereby, the force indicated by Fz, which is caused by the tensile load, is best introduced into the cellular concrete material surrounding the screw 1. This is because the component force Fa is generated at a relatively gentle angle γ of about 30 ° with respect to the plane 11 perpendicular to the screw axis 10.

In a consistently cylindrical screw shaft 2, the aerated concrete material has a core section 1 because the core section 12 of the thread section 5 is formed cylindrically between the thread flanks.
Make sure to surround the entire circumference of 2. Depending on the shape of the thread flank 7, the cylindrical core section 12 extends over a narrow or wide area each between two threads, which also extends over a length corresponding to at least half of the thread pitch S. There is.

The above description assumes that the thread flank 7 is formed by an arcuate generatrix with a radius of curvature R. However, it is also conceivable that the generatrix of the thread flank 7 shifts to the core in a parabolic shape. Furthermore, the extension of the busbars of the thread flank 7 may be formed from a number of linear or curved sections, possibly stepwise connected to one another. However, even in this case, the bus bar formed in this way is also formed substantially along an arc or a parabola.

The pull-out resistance of the screw according to the invention is significantly improved over the known construction, a more economical production is possible with a comparatively low material cost, and a relatively large amount of aerated concrete material is provided between the threads. It becomes possible to take in. Due to the relatively slight material pressure when screwing in such a screw, the explosive effect in the cellular concrete material is also prevented.

The pull-out resistance value improved by the special construction of the screw as described above can be clearly read from the following comparison table.
This table shows the average value of several experimental results. In this comparison table, a screw having the thread shape of the present invention shown in FIGS. 1 to 3 and a known screw thread having the thread shapes shown in FIGS. 4, 5, and 6 are known. Compared with screws.

In this experiment, the threads had the following common and consistent dimensions: Core diameter 5mm Outer diameter 8mm Thread pitch 5.8mm Thread length 60mm Thread depth 80mm In the above description, the asymmetrical structure is obtained due to the special construction of the thread profile. Having a symmetrical thread profile can be advantageous in some cases for thread making or rolling, so that the asymmetric thread profile extends over most of the thread section and the tip 4
Only the first one-pitch thread following the may have a symmetrical thread profile. If desired, the first one-and-a-half screw thread following the cutting edge 4 may have a symmetrical thread profile.

According to another embodiment of the screw 1, the outer diameter of the thread section 5 of the screw shaft 2 and the core diameter are from the cutting edge 4 to the screw head 3.
It expands in a conical shape. Therefore, the core sections 12 are each conical or frustoconical between the two threads, rather than cylindrical. Even in such a case, the ratio of the outer diameter to the core diameter and the thread pitch over the entire length of the screw shaft 2 are constant. This configuration is advantageous for securing the screws within the cellular concrete as the cellular concrete material surrounding the screws is more compacted as the screws are screwed deeper.

FIG. 1 shows a countersunk screw head 3 with an engagement opening for a hexagon spanner. The configuration of the screw head 3 can be selected differently depending on the purpose of use of the screw 1. Only the special configuration of the thread is important, especially since this screw must be adapted to be screwed into cellular concrete.

[Brief description of drawings]

The drawings show an embodiment of the self-tapping pin screw of the present invention. FIG. 1 is a side view of the screw according to the present invention, and FIG.
FIG. 3 is an enlarged view of the detail A according to the drawing, FIG. 3 is a partially enlarged view of the thread section of the screw according to FIG. 1, and FIGS. 4 to 6 are views showing the thread section of a known screw. 1 ... screw, 2 ... screw shaft, 3 ... screw head,
4 ... Destination, 5 ... Thread classification, 6 ... Classification, 7 ...
Thread flank, 8 ... Thread crest, 9 ... Thread flank, 10 ... Screw axis, 11 ... Plane, 12 ...
Core classification, Da ... Outer diameter, Dk ... Core diameter, Fz ... Force, Fa
…… Result force, R …… Radius of curvature, S …… Pitch of thread, α…
... angle, β ... flank inclination angle, γ ... angle

Claims (6)

[Claims] 1. A self-tapping screw for screwing into cellular concrete, having an outer diameter of at least 1.5 times the core diameter, wherein the thread profile limited by two busbars is a screw thread. Of a type that is asymmetric with respect to a plane perpendicular to the axis of the, the generatrix of the thread flank (7) facing the screw head (3) is at least partially from the crest of the thread (8) to the core ( 12)
Extending in an arc or parabola up to, or in some cases connected to each other in steps, and formed of a number of straight or curved sections extending in a generally arc or parabola, the point (4) The generatrix of the thread flank (9) facing toward is substantially perpendicular to the screw axis (10) (1
Self-tapping screw for screwing into cellular concrete, characterized in that it is formed by a straight line forming an angle of approximately 0 to 25 ° with respect to 1). 2. The mean inclination angle (β) of the generatrix of the thread flank (7) facing the screw head (3) is the axis of the screw (1).
A screw according to claim 1, characterized in that it makes an angle of approximately 60 ° with respect to a plane (11) perpendicular to 0). 3. Screw according to claim 1, characterized in that the core (12) of the thread section of the screw shaft (2) is cylindrically arranged between adjacent threads (5). . 4. The cylindrical core (12) extends between two adjacent threads (5) over at least half the length of the thread pitch (8). The screw according to 1. 5. From the claim 1 characterized in that the outer diameter and the core diameter of the thread section of the screw shaft (2) increase conically from the cutting edge (4) to the screw head (3). Four
The screw according to any one of 1 to 6 above. 6. Screw according to claim 5, characterized in that the ratio of the outer diameter of the thread section of the screw shaft (2) to the core diameter is constant over the entire length of the thread section.